SCOTLAND'S native tree population is at threat from global warming, with some species migrating north for more suitable conditions, according to forestry experts.

Forests and woodlands in the south of the country are seeing some trees disappear and being replaced over time with trees themselves migrating north from England. Some of the most common trees in Scotland - the juniper, aspen, and alder - have been in decline in the south of the country, according to the Central Scotland Forest Trust.

They are flourishing in the north, but south of the central belt they are being replaced by beech, lime, and horse chestnut, trees commonly native to England.

Changes in temperature and rainfall, leading to changing forest conditions, are believed to be the cause of the altering of the scenery in many woodland areas.

Simon Rennie, chief executive of the trust, said the migration has been a slow process over the past 30 years.

He said: "There has always been some of these trees in the north, the growing conditions are better. There is still woodland in the south, but it will be different. We can expect wildlife changes as changes in plant life affect the wildlife who inhabit the woodland."

The trust has planted 13 million trees over 60,000 hectares in the past 10 years to help offset CO 2emissions. Mr Rennie said trees were a key weapon in tackling the negative aspects of Scotland's industrial activity, both past and present.

He added: "There is a tendency to be blase about global warming. We are all guilty of assuming it is not our problem as the effects are not always apparent in people's everyday lives. The sad fact is that these effects will present themselves a lot sooner than we think if we continue to abuse our planet."

Mr Rennie warned thriving woodlands were essential for thriving rural communities. "Increasing the number of native trees in this area not only substantially improves its appearance but has a positive effect on the health and quality of life of its inhabitants.

"Where the landscape is sparse or unattractive, fewer people will be inclined to indulge in healthy leisure activities in the open air. But, if people have pride in their local surrounding area, they are more likely to get out and about."

Migrating trees is the latest natural change in Scotland to be laid at the door of global warming. The grouse shooting season has been hit this year by falling stocks, believed to be the result of higher temperatures allowing gut parasites to thrive in mild winters, killing thousands of birds.

Sightings of killer whales and minke whales in the north of Scotland have doubled in the past year with higher sea temperatures thought to be bringing them closer to the shore.